Pipe tee

ABSTRACT

A pipe tee comprises a substrate having deposited thereon a reinforcing wrapping of a resin-impregnated filament.

BACKGROUND OF THE INVENTION

In one aspect, the invention relates to a pipe tee. In another aspect,the invention relates to improvements to a pipe tee. In yet anotheraspect, the invention relates to a process for forming a plastic pipetee.

Plastic pipe has come into extensive use in recent years for handlingcorrosive materials, petrochemicals, and the like where metallic pipe isunsuitable; and other applications where metallic pipe is undulyexpensive. The plastic pipe itself, which can be formed from a suitablethermoplastic material such as polyethylene, is usually extruded fromhigh throughput machines.

Plastic pipe fittings for such pipes up to a pipe diameter of about 8inches are usually injected molded. Such fittings are small and havegood stress ratings and can be made economically on commerciallyavailable equipment. The larger pipe fittings, such as for pipes havinga diameter from about 10 inches up to about 48 inches, are too expensiveto made by injection molding since they require massive equipment andextremely high mold costs. Rotationally molded fittings can be made atconsiderably lower cost do to the less expensive equipment requirements.However, when pipe fittings are rotationally molded, it is extremelydifficult to control the wall thickness of the fitting so as to providesufficient strength at the areas of greatest stress. It is particularlydifficult to rotationally mold large diameter pipe fittings to have longterm hoop stress resistance equal to the long term hoop stressresistance of the plastic pipe to which it is to be attached.Additionally the heavy walls require extremely long cycle times and donot develop good gel on the inside surfaces. Further the heavy wall isdifficult to mold without bubbles, which can lead to premature failure.

It will be extremely desirable to solve these molding problems andprovide long term hoop stress resistance in the fitting equal to thelong term hoop stress resistance in the piping system; to mold thinnerwall pipe fittings; and to reinforce pipe fittings by economicalmethods.

OBJECTS OF THE INVENTION

It is thus an object of this invention to provide a pipe fitting whichis reinforced so as to require only small amounts of material in thewalls, and to be suitable for fabrication by rotational molding.

It is another object of this invention to provide a reinforced pipefitting which utilizes only small amounts of the reinforcing material.

It is a further object of this invention to provide a method forreinforcing of pipe fitting which is readily adapted for automation andprovides economical results.

SUMMARY OF THE INVENTION

In one aspect of the present invention, there is provided a suitablesuitable substrate defining a branched pipe fitting which was depositedthereon a reinforcing wrapping of resin impregnated filament rovings.The wrapping of resin impregnated filament rovings providesreinforcement to the pipe fitting and allows for the use of a thinnerwalled substrate. Additionally, the filament rovings can be deposited onselected pipe fittings when their end use is to be for relatively highpressure service.

In another aspect of the present invention, a plastic pipe tee isprovided having a straight run with the straight run having a back side,a front side opposite from the back side, a first hand side between theback side and the front side, and a second hand side opposite to thefirst hand side, the first hand side bearing a branch which divides thestraight run into a first end portion and a second end portion with theintersection between the branch and the straight run passing through afirst apex point on the first hand side and a second apex point on thesecond hand side, each of the first apex point and the second apex pointbeing a point at which a line following the exterior surface of thestraight run is tangent to the intersection of the branch and thestraight run, the back side of the run have a center point on itssurface which is coaxial to the axis of the branch. Onto the run of thispipe tee, there is deposited one or more circuits of a wrappingcharacterized by a combination of six helical wraps. The first wrapextends from the front side of the first end portion across the firsthand side, the center point of the back side, the second hand side andto the front side of the second end portion. The second wrap extendsfrom the front side of the second end portion, across the first handside, the center point of the back side, the second hand side and to thefront side of the first end portion. The third wrap extends from thefront side of the first end portion across the first apex point on thefirst hand side and to the back side of the second hand portion. Thefourth wrap extends from the back side of the second end portion, acrossthe second apex point on the second hand side, and to the front side ofthe first end portion. The fifth wrap extends from the back side of thefirst end portion, across the second apex point of the second hand side,and to the front side of the second end portion. The sixth wrap extendsfrom the front side of the second end portion, across the apex point ofthe first hand side, and to the back side of the first end portion.Where the wrapping has a relatively narrow width relative to the widthof the branch, reinforcement will require minimal amounts of materialwhile adequate reinforcement will be provided to the areas of the pipemost prone to pressure induced failure. This reinforced pipe tee can beproduced by continuously winding one or more circuits of the wrappingfollowing a path beginning on the front side of the first end portionand extending from the front side of the first end portion angularlyacross the first hand side, the center point of the back side, thesecond hand side, angularly crossing to the front side of the second endportion and circumferentially around the second end portion at leastonce, then continuing along a second wrap extending from the front sideof the second end portion, angularly across the first hand side, thecenter point of the back side, the second hand side and angularlycrossing to the front side of the first end portion andcircumferentially around the first end portion at least once; thencontinuing along a third wrap extending from the front side of the firstend portion angularly across the apex point of the first hand side tothe back side of the second end portion and around the second endportion at least once; then continuing along a fourth wrap extendingfrom the back side of the second end portion angularly across the apexpoint of the second hand side, to the front side of the first endportion and circumferentially around the first end portion at leastonce; then continuing along a fifth wrap extending from the back side ofthe first end portion, across the apex point of the second hand side, tothe front side of the second end portion and circumferentially aroundthe second end portion at least once; then continuing along a sixth wrapextending from the front side of the second end portion angularly acrossthe apex point of the first hand side to the back side of the first endportion. The method is readily automated since the wrapping can beformed from continuous filament rovings and thus can be utilized toprovide extremely economical results.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 and 2 are pictorial representations of an unwrapped tee labeledwith the nomenclature used in the application.

FIGS. 3-11 illustrate sequentially the wrapping steps utilized inaccordance with the preferred embodiment of the present invention.

FIG. 12 is an elevational view of a pipe tee according to one embodimentof the present invention.

FIG. 13 is a bottom view of the embodiment shown in FIG. 12 when viewedalong the indicated lines 13--13.

FIG. 14 is a pictorial view of a flanged pipe tee encased with resinimpregnated fabric.

FIG. 15 is a pictorial view of the flanged tee of FIG. 14 with aplurality of circuits of wraps according to the invention and aplurality of circular wraps around the branch.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIGS. 12 and 13, the preferred embdiment of the inventionis broadly a branched pipe fitting 2, the wall of which is formed from asuitable substrate encased in one or more layers of resin impregantedfabric, hereinafter described and having deposited thereon a reinforcingwrapping 4 of a resin impregnated filament roving 6. The fitting 2 canbe formed from any suitable substrate. Preferably, the branched pipefitting 2 is formed from a thermoplastic material, such as crosslinkablepolyethylene. More preferably, the branched pipe fitting 2 is in theform of a pipe tee where the branch intersects the run at an angle ofabout 90° because pipe tees have been tested with good results. Otherbranched pipe fittings, such as Y-shaped fittings, can also bestrengthened according to the invention. Generally the pipe tee will beformed by a rotational molding process because rotational molding is themost economical way to form pipe tees having a large diameter such as inthe range from about 10 inches to about 48 inches.

The reinforcing wrapping of filament preferably contains fiberglassrovings. A suitable filament roving is PPG Glass Roving No. 1062T250.This glass roving has a weight of about 247 yards per pound and containsfour rovings. The resin with which the filament is impregnated isgenerally selected from resins which use a curing agent, such as epoxyresins, polyester resins, or polyurethane resins. Epoxy resin ispreferred, such as Shell Epon 828, which has been used with goodresults. This resin can be cured with Apco 2170 amine-type hardner andoptionally oven cured at an elevated temperature such as about 300° F.for a few hours to complete curing.

FIGS. 1 and 2 illustrate a branched pipe fitting in the form of a pipetee 2 which is preferably formed from a plastic substrate. The pipe tee2 has a straight run 8, and a branch 18 which intersects the run at anangle of about 90° and divides the straight run into a first end portion20 and a second end portion 22. Each end portion has a back side 10, afront side 12 opposite from the back side 10, a first hand side 14between the back side 10 and the front side 12 and a second hand side 16opposite to the first hand side 14.

As between FIGS. 1 and 2, the pipe tee has been rotated about the axisof branch 18 by an angle of about 90° in the counterclockwise direction.In FIG. 1, second hand side 16 of straight run 8 is illustrated, whilein FIG. 2, first hand side 14 of straight run 8 is illustrated. Thisrelationship is repeated as between FIGS. 3 and 4, FIGS. 5 and 6, FIGS.7 and 8, and FIGS. 14 and 15.

The branch 18 and the run 8 intersect at a saddle shaped intersection24. The intersection 24 passes through a first apex point 26 on thefirst hand side 14 of the straight run 8 and a second apex point 28 onthe second hand side 16 of the straight run 8. The apex point on each ofthe first side 14 and the second side 16 is the point at which a linefollowing the surface of the straight run 8 is tangent to theintersection 24 of the branch 18 and the straight run 8. The back side10 of the straight run 8 has a center point 30 which is opposite to thebranch 18. This is most clearly shown in FIG. 13.

In accordance with one embodiment of the invention, the plastic pipe tee2 has deposited on it one or more circuits of a wrapping 4 comprising acombination of six helical wraps extending between the first end portion20 and the second end portion 22.

As shown best in FIGS. 3 and 4, the first wrap 32 extends from the frontside 12 of the first end portion 20 across the first hand side 14, thecenter point 30 of the back side 10, the second hand side 16 and to thefront side 20 of the second end portion 22. If desired, the wrapping 4can then extend around the second end portion 22 at least oncecircumferentially.

As shown best in FIG. 5, a second wrap 33 extends from the front side 12of the second end portion 22, across the first hand side 14, the centerpoint 30 of the back side 10, the second hand side 16 and to the frontside 12 of the first end portion 20. If desired, the wrapping can thenextend circumferentially around the first end portion 20 at least once.

In FIGS. 6 and 7, a third wrap 34 extends from the front side 12 of thefirst end portion 20, across the first apex point 26 on the first handside 14, and to the back side 10 of the second end portion 22 as bestshown in FIG. 7. If desired, the wrapping can then extend at least oncecircumferentially around the second end portion 22 as illustrated inFIG. 8 for example.

Referring to FIG. 9, a fourth wrap 36 extends from the back side 10 ofthe second end portion 22, across the second apex point 28 on the secondhand side 16, and to the front side 12 of the first end portion 20. Thewrapping can then, if desired, extend at least once circumferentiallyaround the first end portion 20 and preferably extends around the firstend portion 20 one and one-half times.

Referring to FIG. 10, a fifth wrap 38 extends from the back side 10 ofthe first end portion 20, across the second apex point 28 of the secondhand side 16, and to the front side 12 of the second end portion 22. Thewrapping can then extend at least once circumferentially around thesecond end portion 22.

Referring to FIG. 11, a sixth wrap 40 extends from the front side 12 ofthe second end portion 22, across the first apex point 26 of the firsthand side 14 and to the back side 10 of the first end portion 20. Thewrapping can then extend partially or fully around the first end portion20.

Referring to FIGS. 12 and 15, a circular wrap 50 comprising six circuitsextends around the branch 18 of the tee. Preferably the wrap 50 iscomprised of the same material as wrap 4. End portions 20 and 22 can beprovided with a similar circular wrap if desired.

Preferably, as best shown by FIG. 14, for example, the plastic pipe tee2 further comprises one or more layers 42 of resin-impregnated fabric 42encasing the portion of the branch 18 adjacent the run 8 and theportions of the first end portion 20 of the run 8 and the second endportion 22 of the run 8 which are adjacent to the branch 18. Any desirednumber of layers of fabric 42 can be utilized. The resin-impregnatedfabric will generally comprise about 30-50 wt.% fabric and about 50-70wt.% resin. Preferably, where the pipe has a diameter in the range offrom about 10 to about 48 inches, from about 1 to about 10 layers offabric such as woven glass cloth will be used, usually from about 2 toabout 6 layers of resin impregnated fiberglass fabric. A suitablefiberglass cloth is J. P. Stevens No. 7520, 8.70 oz./yds.², which is a0.012 inches thick plain weave, 180 mesh plain weave glass cloth.Preferably the glass cloth is wrapped on the tee 2 so that the warp andweft yarns of the glass fabric will be substantially followed by therovings in the third wrap, the fourth wrap, the fifth wrap, and thesixth wrap. For an 8 inch inside diameter flanged pipe tee formed ofcrosslinkable polyethylene having a diameter to wall thickness ratio of15.5:1 and designed for 210 psig service, three layers of resinimpregnated fiberglass cloth were used with good results. For an 8 inchflanged pipe tee formed from crosslinkable polyethylene with a diameterto side ratio of 11:1 designed for 320 psig service, five layers of theresin impregnated fiberglass cloth were with good results. The resinimpregnated fiberglass cloth so used contained about 40% by weight glassand about 60% by weight polyester resin. The polyester resin tested withgood results was formed from Shell Epon 828 about 76% by weight, TETA(triethylene tetraamine) approximately 7% by weight, and Apco 2170,which is a cyanoethyl modified aliphatic amine, about 17% by weight.Apco 2170 is commercially available from Applied Plastics Company of ElSegundo, Calif.

Preferably, the wrapping comprises from about 1 to about 25 circuits ofresin impregnated filament rovings. Each circuit is preferably formedfrom filament rovings because filament rovings are readily adapted formachine lay up. The wrapping preferably follows a path beginning on thefront side 4 of the first end portion 20 and extending around the firstend portion 20 at least once circumferentially then along the first wrapaforementioned from the front side 10 of the first end portion 20angularly across the first hand side 14 and the center point 30 of theback side 10 to the front side 12 of the second end portion 22. Thewrapping then preferably extends circumferentially around the second endportion 22 at least once. From the front side 12 of the second endportion 22, the wrapping then continues along the second wrap angularlyacross the first hand side 14 and center point 30 of the back side 10 tothe front side 12 of the first end portion 20. The wrapping then extendspreferably circumferentially around the first end portion 20 at leastonce. The path then continues along the third wrap from the front side12 of the first end portion 20 angularly across the first apex point 26of the first hand side 14 and to the back side 10 of the second endportion 22. Preferably, the wrapping then extends circumferentially atleast once around the second end portion 22 then continues along thefourth wrap from the back side 10 of the second end portion 22 angularlyacross the second apex point 28 of the second hand side 16 and to thefront side 12 of the first end portion 20. The wrapping then extendspreferably circumferentially around the first end portion 20 at leastonce and then continues along the fifth wrap from the back side 10 ofthe first end portion 20 across the second apex point 28 of the secondhand side 16 to the first side 10 of the second end portion 22 and thenpreferably circumferentially around the second end portion 22 at leastonce. The path then continues along the sixth wrap from the front side12 of the second end portion 22 angularly across the first apex point 26of the first hand side 14 to the back side 10 of the first end portion20 and then ending at a point partially or fully around the first endportion 20.

More preferably from about 5 to about 20 circuits of the filament areutilized in forming the wrapping or girdle. The filament will generallycomprise a plurality of substantially parallel fiberglass rovings andhave a width in the range from about 5% to about 25% of the diameter ofthe branch 18 of the tee 2. Fiberglass tape can be used if desired.Sufficient resin, preferably of the aforementioned type, is utilized inconjunction with the fiberglass filament rovings to provide the resinimpregnated filament rovings in the range of from about 60 to about 70%by weight glass and from about 40 to about 30% by weight resin. ShellEpon 828 resin has been used with good results. In a preferredembodiment, the wrapping or girdle comprises about 5 to 20 circuits of afilament having four rovings and about a 1/2 inch band width whendeposited on the tee. A filament roving which has been used with goodresults is 1062T15 filament available from Pittsburgh Paint and Glassand has a weight of about 247 yards per pound.

In a preferred embodiment, the pipe tee 2 further comprises a pluralityof circumferentially extending circular resin impregnated filament wrapson the branch 18, the first end portion 20, and the second end portion22. These wraps provide the tee 2 with additional resistance to hoopstress and aesthetically improve its appearance. The filament rovingscan be the same as utilized for the girdle.

Preferably, the pipe tee having the winding deposited thereon is heatedto a temperature in the range from about 250° to about 350° F. for aperiod of time of from about 1 to about 24 hours or more to acceleratethe cure of the resin. The invention is illustrated by the followingexample:

EXAMPLE

Flanged pipe tees of 8" nominal diameter were made by rotationalmolding, a method known in the art, from Marlex CL-100 L618 which is acrosslinkable ethylene-hexene copolymer furnished by Phillips ChemicalCo. of Bartlesville, Okla. The samples had a 0.75" sidewall thickness.Ten of the samples were wrapped as described in the specification withfive layers of woven glass cloth, J. P. Stevens #7520, 8.70 oz/yd²,0.12" thickness, plain weave and fifteen circuits of Pittsburgh Paintand Glass Co. #1062T15, 15 strand, 247 yield (yds/lb) fiberglass typesaturated with resin comprised by weight of 76% Shell Epon 828, 7%trethylene tetra amine, and 17% Apco 2170 (cyanoethyl modified aliphaticamine), sold by Applied Plastics Co. of Segundo, Calif. Fifteen sampleswere not wrapped. All samples had steel blind flanges attached on thethree openings and were hydrostatic tested at the pressures shown in thetable. The samples were maintained at room temperature of about 73° F.at the indicated pressure until failure or termination of the test.

    ______________________________________                                        Wrapped Tees                                                                               Gauge                                                            Sample #     Pressure PSI                                                                             Hours on Test.sup.1                                   ______________________________________                                        1            360        144*.sup.2                                            2            360        26,000+                                               3            320        26,000+                                               4            320        26,000+                                               5            280        26,000+                                               6            280        26,000+                                               7            250        13,000+                                               8            250        13,000+                                               9            200        13,000+                                               10           200        13,000+                                               ______________________________________                                         .sup.1 Test terminated without failure.                                       *.sup.2 This sample was not molded properly. It failed @ 144 hours.      

    ______________________________________                                        Non-Wrapped Tees                                                                            Hours to Failure                                                ______________________________________                                        11           360     14                                                       12           360     192                                                      12           360     96                                                       14           330      7                                                       15           330     528                                                      16           320     168                                                      17           320    1560                                                      18           300     408                                                      19           300     384                                                      20           300     672                                                      21           280     908                                                      22           280     672                                                      23           280    1532                                                      24           260    1152                                                      25           260    2184                                                      26           250     888                                                      27           250    1008                                                      28           250    3096                                                      29           230    1416                                                      30           230     960                                                      31           230    1152                                                      32           200    3144                                                      33           200    2616                                                      34           200    5208                                                      35           150    4056                                                      36           150    5928                                                      ______________________________________                                    

It can be seen from the preceding Table that the wrapping provided aconsiderable improvement in long term hoop stress.

What is claimed is:
 1. A plastic pipe tee having a straight run, thestraight run having a back side, a front side opposite from the backside, a first hand side between the back side and the front side, and asecond hand side opposite to the first hand side, wherein the front sidebears a branch which divides the straight run into a first end portionand a second end portion and the intersection between the branch and thestraight run passes through a first apex point on the first hand sideand a second apex point on the second hand side, each of the first apexpoint and the second apex point being the point at which a straight linefollowing the surface of the straight run is tangent to the intersectionof the branch and the straight run, the back side having a center pointwhich is opposite to the branch, said plastic pipe tee having depositedthereon one or more circuits of a winding comprising a combination of 6helical wraps extending between the first end portion and the second endportion;wherein the first wrap extends from the front side of the firstend portion across the first hand side, the center point of the backside, the second hand side and to the front side of the second endportion; wherein the second wrap extends from the front side of thesecond end portion, across the first hand side, the center point of theback side, the second hand side and to the front side of the first endportion; wherein the third wrap extends from the front side of the firstend portion across the first apex point on the first hand side and tothe back side of the second end portion; wherein the fourth wrap extendsfrom the back side of the second end portion, across the second apexpoint on the second hand side, and to the front side of the first endportion; wherein the fifth wrap extends from the back side of the firstend portion, across the second apex point of the second hand side, tothe front side of the second end portion; and wherein the sixth wrapextends from the front side of the second end portion, across the apexpoint of the first hand side, and to the back side of the first endportion.
 2. A plastic pipe tee having a straight run, the straight runhaving a back side, a front side opposite from the back side, a firsthand side between the back side and the front side, and a second handside opposite to the first hand side, wherein the front side bears abranch which divides the straight run into a first end portion and asecond end portion and the intersection between the branch and thestraight run passes through a first apex point on the first hand sideand a second apex point on the second hand side, each of the first apexpoint and the second apex point being the point at which a straight linefollowing the surface of the straight run is tangent to the intersectionof the branch and the straight run, the back side having a center pointwhich is opposite to the branch, said plastic pipe tee having depositedthereon one or more layers of a resin-impregnated woven glass fabrichaving warp and weft yarns, said fabric encasing the portion of thebranch adjacent the run and the portions of the first end portion andthe second end portion adjacent the branch, wherein the layers compriseabout 30-50% by weight glass and about 50-70% by weight resin; andone ormore circuits of a winding comprising a combination of 6 helical wrapsextending between the first end portion and the second end portion;wherein the first wrap extends from the front side of the first endportion across the first hand side, the center point of the back side,the second hand side and to the front side of the second end portion;wherein the second wrap extends from the front side of the second endportion, across the first hand side, the center point of the back side,the second hand side and to the front side of the first end portion;wherein the third wrap extends from the front side of the first endportion across the first apex point on the first hand side and to theback side of the second end portion; wherein the fourth wrap extendsfrom the back side of the second end portion, across the second apexpoint on the second hand side, and to the front side of the first endportion; wherein the fifth wrap extends from the back side of the firstend portion, across the second apex point of the second hand side, tothe front side of the second end portion; and wherein the sixth wrapextends from the front side of the second end portion, across the apexpoint of the first hand side, and to the back side of the first endportion.
 3. A plastic pipe tee as in claim 2 wherein the warp and weftyarns of the glass fabric substantially follow the winding along thethird wrap, the fourth wrap, the fifth wrap and the sixth wrap.
 4. Aplastic pipe tee as in claim 3 further comprising a plurality ofcircumferentially extending circular resin-impregnated wraps on thebranch, the first end portion and the second end portion.
 5. A plasticpipe tee as in claim 4 wherein the combination of 6 helical wrapscomprising a circuit of winding are formed from a continuous rovingfollowing a path beginning on the front side of the first end portionand extending around the first end portion at least oncecircumferentially, then continuing along a first wrap from the frontside of the first end portion angularly across the first hand side andthe center point of the back side to the front side of the second endportion and circumferentially around the second end portion at leastonce; then continuing from the front side of the second end portionalong a second wrap angularly across the first hand side and centerpoint of the back side to the front side of the first end portion andcircumferentially around the first end portion at least once; thencontinuing along a third wrap from the front side of the first endportion angularly across the first apex point of the first hand side andto the back side of the second end portion and circumferentially aroundthe second end portion at least once, then continuing along a fourthwrap from the back side of the second end portion angularly across thesecond apex point of the second hand side and to the front side of thefirst end portion and circumferentially around the first end portion atleast one and one-half times, then continuing along a fifth wrap fromthe back side of the first end portion angularly across the second apexpoint of the second hand side to the front side of the second endportion and circumferentially around the second end portion at leastonce, then continuing along a sixth wrap from the front side of thesecond end portion angularly across the first apex point of the firsthand side to the back side first end portion and circumferentiallyaround the first end portion at least once.
 6. A plastic pipe tee as inclaim 5 wherein the wrapping comprises from 1 to about 25 circuits of anepoxy resin-impregnated plurality of glass rovings comprising in a rangeof 60% to 70% by weight glass and 40% to 30% by weight resin.
 7. Aplastic pipe tee as in claim 4 wherein the wrapping is formed from aplurality of fiberglass rovings and has a width in the range of fromabout 5% to about 25% of the diameter of the branch, and wherein the teehas from about 1 to about 10 layers of fiberglass cloth depositedthereon.
 8. A plastic pipe tee as in claim 7 formed by rotationallymolding crosslinkable polyethylene, laying from about 2 to about 6layers of resin impregnated fiberglass cloth thereon, winding from about5 to about 20 circuits of resin-impregnated fiberglass roving thereon,and curing the resin.
 9. A plastic tee as in claim 8 further comprisinga wrapping on the branch formed from 1 to about 25 circuits of acircular wrap around the branch adjacent to the runs.
 10. A process forwrapping a pipe tee having a straight run, the straight run having aback side, a front side opposite from the back side, a first hand sidebetween the back side and the front side, and a second hand sideopposite to the first hand side, wherein the front side bears a branchwhich divides the straight run into a first end portion and a second endportion the intersection between the branch and the straight run portionpassing through an apex point on the first hand side and an apex pointon the second hand side, each of the apex points being the point atwhich a straight line following the surface of the straight run istangent to the intersection of the branch and the straight run, the backside having a center point which is opposite to the branch;said processcomprising laying one or more circuits of a winding following a pathbeginning on the front side of the first end portion and extendingaround the first end portion at least once circumferentially thencontinuing along a first wrap extending from the front side of the firstend portion angularly across the first hand side, the center point ofthe back side, the second hand side, angularly crossing to the frontside of the second end portion and circumferentially around the secondend portion at least once, then continuing along a second wrap extendingfrom the front side of the second end portion, angularly across thefirst hand side, the center point of the back side, the second hand sideand angularly crossing to the front side of the first end portion andcircumferentially around the first end portion at least once; thencontinuing along a third wrap extending from the front side of the firstend portion angularly across the apex point of the first hand side tothe back side of the second end portion and around the second endportion at least once; then continuing along a fourth wrap extendingfrom the back side of the second end portion, angularly across the apexpoint of the second hand side, to the front side of the first endportion and circumferentially around the first end portion at leastonce; then continuing along a fifth wrap extending from the back side ofthe first end portion, across the apex point of the second hand side, tothe front side of the second end portion and circumferentially aroundthe second end portion at least once; then continuing along a sixth wrapextending from the front side of the second end portion angularly acrossthe apex point of first hand side to the back side of the first endportion and circumferentially around the first end portion at leastonce.
 11. A process as in claim 10 further comprising impregnating thewinding with an epoxy resin.
 12. A process for wrapping a pipe teehaving a straight run, the straight run having a back side, a front sideopposite from the back side, a first hand side between the back side andthe front side, and a second hand side opposite to the first hand side,wherein the front side bears a branch which divides the straight runinto a first end portion and a second end portion the intersectionbetween the branch and the straight run portion passing through an apexpoint on the first hand side and an apex point on the second hand side,each of the apex points being the point at which a straight linefollowing the surface of the straight run is tangent to the intersectionof the branch and the straight run, the back side having a center pointwhich is opposite to the branch;said process comprising laying at leastone thickness of epoxy resin impregnated reinforcing fabric onto thepipe tee with the yarns of the fabric laying at an angle to thedirection of the branch and the straight run; then laying one or morecircuits of a winding following a path beginning on the front side ofthe first end portion and extending around the first end portion atleast once circumferentially then continuing along a first wrapextending from the front side of the first end portion angularly acrossthe first hand side, the center point of the back side, the second handside, angularly crossing to the front side of the second end portion andcircumferentially around the second end portion at least once, thencontinuing along a second wrap extending from the front side of thesecond end portion, angularly across the first hand side, the centerpoint of the back side, the second hand side and angularly crossing tothe front side of the first end portion and circumferentially around thefirst end portion at least once; then continuing along a third wrapextending from the front side of the first end portion angularly acrossthe apex point of the first hand side to the back side of the second endportion and around the second end portion at least once; then continuingalong a fourth wrap extending from the back side of the second endportion, angularly across the apex point of the second hand side, to thefront side of the first end portion and circumferentially around thefirst end portion at least once; then continuing along a fifth wrapextending from the back side of the first end portion, across the apexpoint of the second hand side, to the front side of the second endportion and circumferentially around the second end portion at leastonce; then continuing along a sixth wrap extending from the front sideof the second end portion angularly across the apex point of first handside to the back side of the first end portion and circumferentiallyaround the first end portion at least once.
 13. A process as in claim 12further comprising laying one or more bands of resin-impregnatedfiberglass rovings circumferentially around the branch, the first endportion, and the second end portion.